Brendan J. Tunstall, PhD

Education and Training

• Bachelor of Behavioural Neuroscience (Honours), Monash University, Australia (2008)
• PhD in Behavior, Cognition, & Neuroscience, American University, Washington, DC (2014)
• Post-doctoral Research Fellow, National Institute on Drug Abuse, Baltimore, MD (2015-2021)

Research Interest

The goal of my research is to better understand the neurobiological mechanisms that drive drug taking and seeking.

Neurobiology of alcohol dependence

My current research aims to define the role of consummatory- and stress-related neuropeptides in alcohol dependence. I recently determined that administration of the neuropeptide oxytocin blocked the escalated drinking that develops in alcohol-dependent rats (including administration by intranasal route, a technique also applied in humans). It is my hope that with a combination of behavioral, in vivo neurobiological (e.g., optogenetics and fiber photometer), and microscopy techniques, that I will be able to elucidate the brain signaling elements involved in this phenomenon.

Neurobiology of opioid dependence

During my post-doctoral training, I was involved in the successful development of several novel models of opioid dependence. First, the inhalation of vaporized opioids in rats (i.e., fentanyl and fentanyl analogues), that allows fast brain-exposure to potent and addictive drugs without the requirement of intravenous surgery. We demonstrated the development of opioid addiction-like behaviors in rats that were offered long-access sufentanil self-administration sessions compared to rats that were offered short-access sessions. A major advantage of this approach is that there is no experimental time-window imposed by catheter patency, allowing for longitudinal studies. In a follow-up study, I led the implementation of a behavioral economics approach to demonstrate that rats will develop more “inelastic” demand for fentanyl vapor following extended access self-administration sessions (i.e., will work harder to defend their baseline consumption). I was additionally involved in separate projects in which we demonstrated that mice allowed long-access vs. short-access sessions of intravenous heroin self-administration, or fentanyl vapor self-administration, developed addiction-like behaviors including an escalation of drug intake, somatic signs of withdrawal, drug intake despite punishment, and reinstatement of drug seeking. All of these models will support novel studies of the neurobiology of opioid dependence. I will continue to implement and further develop these models of opioid self-administration and opioid dependence in my own lab.

Role of drug cues in motivation for drugs

Throughout my research career, I have also studied the contribution of drug-associated environmental stimuli to drug-taking and -seeking behavior. By implementing principles of behavioral learning, it has been possible to test and manipulate the long-lasting motivational power held by drug-associated stimuli. In my dissertation work, I used a novel model of reinstatement within a choice situation, to determine that cocaine stimuli are exceptionally strong motivators of reinstatement behavior. Cue-induced cocaine seeking could even be stronger than cue-induced food seeking, although the same rats had earlier demonstrated a preference for food pellets over cocaine injections. I am particularly interested in applying neurobiological techniques to understand the mechanisms underlying these kinds of seemingly paradoxical features of drug-motivated behavior.

Publications

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